Forming jaw for producing a succession of sealed packages from a tube of sheet packaging material

ABSTRACT

A forming jaw for producing a succession of sealed packages from a tube of sheet packaging material filled with a pourable food product and fed in a direction parallel to its longitudinal axis is disclosed. The jaw includes sealing structure that seals a cross section of the tube; and forming structure that imparts a predetermined shape to the tube between two successive sealed cross sections. The forming structure has first and second surfaces for interacting with the tube and which extend respectively in a direction crosswise to, and in a direction parallel to, the axis of the tube. The first surface has a convex portion which exerts pressure on, to control filling of, the packages being formed.

TECHNICAL FIELD

The present invention relates to a forming jaw for producing asuccession of sealed packages from a tube of sheet packaging materialfilled with a pourable food product.

More specifically, the present invention relates to a forming jaw whichmay be used on packaging machines for continuously producing sealedpackages of pourable food products from said tube of packaging material.

BACKGROUND ART

Many pourable food products, such as fruit juice, pasteurized or UHT(ultra-high-temperature treated) milk, wine, tomato sauce, etc., aresold in packages made of sterilized packaging material.

A typical example of such a package is the parallelepiped-shaped packagefor liquid or pourable food products known as Tetra Brik Aseptic(registered trademark), which is produced by folding and sealing a webof laminated packaging material. The packaging material has a multilayerstructure comprising a layer of fibrous material, e.g. paper, covered onboth sides with layers of heat-seal plastic material, e.g. polyethylene.

In the case of aseptic packages for long-storage products, such as UHTmilk, the packaging material also comprises a layer of oxygen-barriermaterial, defined for example by a sheet of aluminium, which issuperimposed on a layer of heat-seal plastic material, and is in turncovered with another layer of heat-seal plastic material eventuallyforming the inner face of the package contacting the food product.

As is known, such packages are produced on fully automatic packagingmachines, on which a continuous tube is formed from the web-fedpackaging material. The web of packaging material is sterilized on thepackaging machine, e.g. by applying a chemical sterilizing agent, suchas a hydrogen peroxide solution, which, after sterilization, is removed,e.g. vaporized by heating, from the surfaces of the packaging material.

The web of packaging material so sterilized is maintained in a closedsterile environment, and is folded into a cylinder and sealedlongitudinally to form a continuous tube. The tube of packaging materialis fed in a vertical direction parallel to its axis, is filledcontinuously with the sterilized or sterile-processed food product, andis fed through a forming station where two or more pairs of forming jawsact cyclically and successively on the tube to seal it along equallyspaced cross sections and form a continuous strip of pillow packagesconnected to one another by respective transverse sealing bands, i.e.extending in a horizontal direction perpendicular to the tube axis.

More specifically, according to a possible known solution, each pair ofjaws is hinged at the bottom to a slide running up and down along avertical guide parallel to the tube of packaging material, so that, asthe slide moves vertically between a top dead center position and abottom dead center position, the jaws open and close substantially“book-fashion” about the tube of packaging material.

To seal the tube of packaging material transversely, the jaws in eachpair have respective sealing members cooperating with opposite sides ofthe tube and defined, for example, by a heating element for locallymelting the mutually contacting plastic layers of the packagingmaterial, and by one or more pressure members made of elastomericmaterial and for providing mechanical support to grip the tube to therequired pressure.

More specifically, packaging material in which the barrier layer isdefined by a sheet of electrically conducting material, e.g. aluminium,is normally heat sealed by means of a so-called induction heat sealingprocess, in which, when the two jaws are gripped about the tube,electric current is induced in, and locally heats, the aluminium sheet,thus resulting in localized melting of the heat-seal plastic material.

Upon completion of the heat-seal operation, a cutting member—carried,for example, by one of the two jaws—is activated and interacts with thetube of packaging material to cut it along the centerline of thetransverse sealing band and so detach a pillow package from the bottomend of the tube of packaging material. The bottom end is thereforesealed transversely, and, once the slide reaches the bottom dead centerposition, the jaws open to avoid interfering with the upper part of thetube; and the pillow packages are fed to a final folding station wherethey are folded mechanically into the finished parallelepiped shape.

In one known solution described and illustrated, for example, in PatentApplication EP-A-1172299, the sealing members are generally carried byrespective horizontal bar portions of the jaws in each pair, which,above the bar portions, have respective open-fronted, C-section formingtabs which, following heat sealing by the relative sealing members,cooperate with each other to define a cavity of given shape and volumeand which encloses and forms the tube of packaging material into arectangular-section configuration.

More specifically, each forming tab comprises an end wall, from whoseopposite lateral edges extend respective parallel lateral walls whichcooperate with respective lateral walls of the other forming tab tosurround the tube of packaging material.

To control filling of the pillow packages being made, the end walls ofeach pair of forming tabs have respective convex portions, which exertpressure on or “squeeze” the lateral walls of the packages to limit theamount of food product in and so obtain the desired weight of eachpackage.

Though fairly effective on the whole, the above package filling controlsystem still leaves room for further improvement.

In particular, in the case of small packages, i.e. with small-arealateral walls, to achieve the desired squeezing effect, convex portionsmust be used which project sharply with respect to the end walls of therelative forming tabs, and which may result in the packages being formedinto unacceptable shapes. Moreover, even using sharply projecting convexportions does not ensure the desired weight of the package.

DISCLOSURE OF INVENTION

It is an object of the present invention to provide a forming jaw forproducing a succession of sealed packages from a tube of sheet packagingmaterial, designed to provide a straightforward, low-cost solution tothe aforementioned drawbacks.

According to the present invention, there is provided a forming jaw forproducing a succession of sealed packages from a tube of sheet packagingmaterial filled with a pourable food product and fed in a directionparallel to its longitudinal axis; said jaw comprising sealing means forsealing a cross section of said tube, and forming means for imparting apredetermined shape to said tube between two successive sealed crosssections; said forming means comprising a first and a second surface forinteracting with said tube and which extend respectively in a directioncrosswise to and in a direction parallel to the axis of the tube;characterized in that said first surface comprises a convex portionwhich exerts pressure on, to control filling of, the packages beingformed.

BRIEF DESCRIPTION OF THE DRAWINGS

A pair of preferred, non-limiting embodiments of the present inventionwill be described by way of example with reference to the accompanyingdrawings, in which:

FIG. 1 shows a schematic side view of a pair of forming jaws inaccordance with the invention, and acting on a tube of sheet packagingmaterial to seal it transversely into a strip of sealed packages;

FIG. 2 shows a partly sectioned, larger-scale side view of a detail inFIG. 1;

FIG. 3 shows a larger-scale view in perspective of a portion of one ofthe jaws in FIG. 1; and

FIG. 4 shows a schematic side view of a forming station comprising anumber of forming jaws in accordance with a different embodiment of thepresent invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Number 1 in FIG. 1 indicates as a whole a forming station for producinga succession of sealed packages 2 of a pourable food product, such aspasteurized or UHT milk, fruit juice, wine, etc.

More specifically, station 1 may be incorporated in a packaging machine(not shown) for continuously producing packages 2 from a tube 3 of sheetpackaging material.

The packaging material has a multilayer structure (not shown), andcomprises a layer of fibrous material, normally paper, covered on bothsides with respective layers of heat-seal plastic material, e.g.polyethylene. In the case of aseptic packages for long-storage products,such as UHT milk, the packaging material also comprises a layer ofoxygen-barrier material, e.g. a sheet of aluminium, which issuperimposed on a layer of heat-seal plastic material, and is in turncovered with another layer of heat-seal plastic material eventuallydefining the inner face of the package contacting the food product.

Tube 3 is formed in known manner upstream from station 1 bylongitudinally folding and sealing a web of heat-seal sheet material, isfilled with the sterilized or sterile-processed food product forpackaging, and is fed by known means (not shown) in a vertical directionparallel to its longitudinal axis A.

As known, for example, from Patent Application EP-A-1172299, station 1interacts with tube 3 to heat seal it at equally spaced cross sectionsinto a vertical strip of pillow packages 2 connected to one another byrespective transverse sealing bands 4. More specifically, station 1 heatseals each sealing band 4 along two parallel sealing lines (not shown),between which the sealing band 4 is then cut in known manner to separatepackages 2.

As shown partly in FIG. 2, the pillow packages 2 produced at station 1each comprise a main portion 5 of the same shape and volume as thefinished—in the example shown, parallelepiped—packages; and transitionportions 6 connecting main portion 5 to the respective adjacent sealingbands 4. Each transition portion 6 is defined by two slightly inclinedpanels 7 extending crosswise to axis A, defining with the relative mainportion 5 a flattened substantially triangular section cavity, andhaving a common edge from which relative sealing band 4 projects. At afollow-up folding station (not shown), the transition portions 6 of eachpillow package 2 are folded onto relative main portion 5, so that panels7 of each transition portion 6 are flattened to form an end wall of thefinished package.

With particular reference to FIG. 1, station 1 comprises, in knownmanner, two pairs of jaws 10 a, 10 b (only one pair of which is shownand described in detail below) which act cyclically and successively ontube 3.

Jaws 10 a, 10 b in each pair are hinged at the bottom to a relativeslide 11 running up and down along a relative vertical guide 12 parallelto tube 3 of packaging material. More specifically, jaws 10 a, 10 b ineach pair extend symmetrically on opposite sides of a vertical plane Pthrough axis A of tube 3, and are hinged to relative slide 11 aboutrespective horizontal axes B so as to open and close substantially“book-fashion” about tube 3 as slide 11 moves up and down.

Guides 12 are located on diametrically opposite sides of tube 3, and arepositioned symmetrically with respect to a plane (not shown)perpendicular to plane P and through axis A of tube 3.

The two pairs of jaws 10 a, 10 b interact alternately with tube 3 ofpackaging material to grip and heat seal it along equally spaced crosssections. The up/down movement of each slide 11 and the opening/closingmovement of jaws 10 a, 10 b are controlled in known manner—notdescribed, by not being necessary for a clear understanding of thepresent invention–by an actuating assembly (not shown) comprising pairsof vertical rods, in turn controlled by rotary cams or servomotors.

Each jaw 10 a, 10 b substantially comprises a main body 15,substantially in the form of a quadrangular plate, which, close to thebottom end, is hinged to relative slide 11 and supports a respectiveprojecting actuating arm 16 cooperating with said actuating assembly.

Jaws 10 a, 10 b also comprise respective supporting arms 17 fixed to thetop ends of respective main bodies 15, and which project from mainbodies 15 in a direction parallel to respective axes B so as to belocated on opposite sides of tube 3.

The projecting portions of supporting arms 17 of jaws 10 a, 10 b arefitted with respective sealing members 18, 19—in the example shown, inthe form of parallelepiped-shaped bars—for interacting with tube 3. Asshown in the accompanying drawings, sealing member 18 may incorporate,for example, an inductor 20 having two straight horizontal activesurfaces 21 for generating current in the aluminium layer of thepackaging material and producing localized Joule-effect melting of themutually contacting plastic layers of the packaging material; andsealing member 19 may incorporate a pair of pressure pads 22 made ofelastomeric material and providing mechanical support to grip tube 3 tothe required pressure at active surfaces 21 of inductor 20.

Above respective sealing members 18, 19, supporting arms 17 of jaws 10a, 10 b are fitted with respective open-fronted, C-section forming tabs23 which, following transverse sealing by relative sealing members 18,19, cooperate with each other to define a cavity of given shape andvolume and which encloses and forms tube 3 into a rectangular-sectionconfiguration.

More specifically, forming tab 23 of each jaw 10 a, 10 b comprises anend wall 24, from whose opposite lateral edges extend respectiveparallel lateral walls 25 which cooperate with respective lateral walls25 of forming tab 23 of the other jaw 10 b, 10 a to surround tube 3 ofpackaging material.

Each forming tab 23 therefore defines a surface 26 for interacting withtube 3 and extending in a direction parallel to axis A of tube 3.

To control filling of pillow packages 2 being made, surfaces 26 of eachpair of forming tabs 23 are advantageously provided, at end walls 24,with respective convex portions 27, which exert pressure on or squeezethe opposite walls of main portion 5 of packages 2.

An important characteristic of the present invention is that each jaw 10a, 10 b also has an additional convex portion 28 projecting from asurface 29, which bounds relative sealing member 18, 19, extendscrosswise to axis A, and faces the opposite way to relative forming tab23. That is, surface 29 constitutes the most downstream portion of eachsealing member 18, 19 in the traveling direction of tube 3.

When forming each package 2, convex portions 28 of each pair of jaws 10a, 10 b press on respective panels 7 of transition portion 6 beingsealed at relative sealing members 18, 19, and, together with the actionexerted by convex portions 27 of the other pair of jaws 10 a, 10 b onmain portion 5 of package 2, squeeze package 2 so to speak to limit theamount of food product in the package and so control the weight of eachpackage 2 leaving station 1 and, consequently, the packaging machine.

According to a different embodiment of the present invention shown inFIG. 4, sealing members 18, 19, provided with respective convex portions28, may be advantageously incorporated in a chain forming unit orstation, indicated as a whole with number 1′, of the type disclosed anddescribed in the European patent application EP-A-0887263, which isincorporated herein by reference, in its entirety.

In particular, as is known, station 1′ essentially comprises a couple ofchain conveyors 30, 31 provided with respective first and second jaws 10a′, 10 b′ (only one pair of which is shown) carrying respective sealingmembers 18, 19 and adapted to cooperate with each other to interact withthe tube 3 of packaging material fed along axis A.

Conveyors 30, 31 define respective endless paths Q and R along whichrespective jaws 10 a′, 10 b′ are fed, and which extend on opposite sidesof axis A.

Each conveyor 30, 31 comprises an articulated chain 32 (only partiallyshown), which extends along the relative path Q, R and whose links aredefined by the respective jaws 10 a′, 10 b′.

Sealing members 18, 19 may be an integral part of the body of therespective jaws 10 a′, 10 b′ or secured thereto.

Similarly to what described and shown relatively to jaws 10 a, 10 b,jaws 10 a′, 10 b′ may be provided, at the top thereof, with respectiveforming tabs 23.

The advantages of forming jaws 10 a, 10 b, 10 a′, 10 b′ according to thepresent invention will be clear from the foregoing description.

In particular, providing convex portions 28 on surfaces 29 of sealingmembers 18, 19 of each pair of jaws 10, 10 b, 10 a′, 10 b′ in additionto convex portions 27 on forming tabs 23 enables accurate control of thesqueezing pressure and final weight of packages 2 being formed, withoutimpairing the shape of the packages. This is mainly due to additionalconvex portions 28 enabling the use of less sharply projecting convexportions 27 on forming tabs 23, thus eliminating the negative effects ofconvex portions 27 interacting with the lateral walls of small packages.

Clearly, changes may be made to forming jaws 10 a, 10 b, 10 a′, 10 b′ asdescribed and illustrated herein without, however, departing from thescope of the accompanying claims.

1. A forming jaw for producing a succession of sealed packages from atube of sheet packaging material filled with a pourable food product andfed in a direction parallel to its longitudinal axis; the jaw comprisingsealing members configured to seal a cross section of the tube, andforming members configured to impart a predetermined shape to the tubebetween two successive sealed cross sections; the forming memberscomprise a first surface and a second surface configured to interactwith the tube and which extend respectively in a direction crosswise to,and in a direction parallel to, the axis of the tube, wherein the firstsurface comprises first and second convex portions which exert pressureon, to control filling of, the packages being formed.
 2. The jaw asclaimed in claim 1, wherein the second surface has a third convexportion which exerts pressure on the packages being formed.
 3. The jawas claimed in claim 1, wherein the sealing members comprise a grippingportion which interacts with the cross sections for sealing of the tube,and defining, at a downstream portion with reference to the travelingdirection of the tube, the first surface.
 4. The jaw as claimed in claim3, wherein the gripping portion comprises a heater operable to heat thepackaging material of the tube.
 5. The jaw as claimed in claim 3,wherein the gripping portion comprises pressure pads.
 6. The jaw asclaimed in claim 5, which comprises a C-shaped forming tab defining,towards the tube, the second surface.
 7. The jaw as claimed in claim 6,wherein the forming tab is located upstream from the gripping portionwith reference to the traveling direction of the tube.
 8. A forming jawfor producing a succession of sealed packages from a tube of sheetpackaging material filled with a pourable food product and fed in adirection parallel to its longitudinal axis; said jaw comprising sealingmeans for sealing a cross section of said tube, and forming means forimparting a predetermined shape to said tube between two successivesealed cross sections; said forming means comprising a first surface anda second surface for interacting with said tube and which extendrespectively in a direction crosswise to, and in a direction parallelto, the axis of the tube, wherein said first surface comprises first andsecond convex portions which exert pressure on, to control filling of,the packages being formed.
 9. The jaw as claimed in claim 1, whereinsaid second surface has a third convex portion for exerting pressure onthe packages being formed.
 10. The jaw as claimed in claim 9, whichcomprises a C-shaped forming tab defining, towards said tube, saidsecond surface having said further third convex portion.
 11. The jaw asclaimed in claim 10, wherein said forming tab is located upstream fromsaid gripping portion with reference to the traveling direction of saidtube.
 12. The jaw as claimed in claim 1, wherein said sealing meanscomprise a gripping portion interacting with the cross sections forsealing of said tube, and defining, at a downstream portion withreference to the traveling direction of the tube, said first surfacefrom which said first and second convex portions project.
 13. The jaw asclaimed in claim 12, wherein said gripping portion incorporates heatingmeans for locally heating the packaging material of said tube.
 14. Thejaw as claimed in claim 12, wherein said gripping portion incorporatespressure means made of elastically yielding material.